This invention relates to an improved follower plate assembly and, more particularly, to the circumferential seal for a follower plate assembly.
To remove fluid materials from containers such as barrels, a common technique is to utilize a mechanical pump in combination with a follower plate assembly. The follower plate fits within the end of the barrel and "follows" the fluid level in the barrel as fluid is withdrawn by means of the pump.
Generally, the follower plate coincides with the shape of the barrel and includes circumferential seals which engage the interior side walls of the barrel. In this manner, movement of the follower plate downward into the barrel may assist in the pumping operation and also provides a means for separating the fluid being pumped from contamination by the atmosphere. In the past, various follower plate designs have been proposed. A typical prior art design is disclosed by FIGS. 1 and 2. With such a design, the circumferential seal for the follower plate comprises one or more hoses which are banded or clamped onto the follower plate. The hoses are made from a rubber material and act as "O ring" seals.
Generally, the banded O ring, hose construction includes a casting or follower with two diametral grooves around the outside diameter of the casting. Two hoses are wrapped around the follower plate and retained in the grooves with metal strapping typically of the type used to band boxes and crates.
This banded hose construction is difficult to make and assemble. The hoses must be cut precisely the right length in order to completely encircle the follower in the associated diametral groove. The hoses must butt together at the ends without leaving a gap. On the other hand, they must not butt too tightly in order to avoid buckling of the hose. The hoses must be retained on the casting by placement of strapping inside of the hose so that the strapping will not scrape on the container wall. Assembly of such a hose construction is difficult. When the seals of such a follower plate assembly do become warn, replacement is complex and time consuming, often requiring complete disassembly of the follower plate.
An alternative to the described construction requires utilization of very large O-ring members. Such O-ring members are made from an elastomeric material and are usually solid. They have limited resiliency. In practice, such O-rings tend to roll out of a follower plate groove. The present invention seeks to overcome these and other problems associated with prior art assemblies.